It has been known to prepare thermoplastic molding compositions from various polymers and rubber latices. These compositions have been prepared by blending the polymers with the grafted rubber or by polymerizing the monomers used to produce the polymer in the presence of the rubber. For example, U.S. Pat. No. 3,354,238 discloses such a molding composition wherein the resinous phase is composed of methylmethacrylate, styrene and acrylonitrile, and the rubber phase is composed of polybutadiene grafted with methylmethacrylate, styrene and acrylonitrile. The compositions of said patent are said to exhibit improved clarity, heat distortion temperature, impact strength, color and gloss. Similarly, U.S. Pat. No. 3,261,887 discloses a molding composition substantially identical to that of the above-discussed patent except that the acrylonitrile is omitted therefrom.
The latter patent exhibits a series of acceptable properties when utilized as a molding composition but exhibits a poor craze resistance and a poor tensile elongation whereas the composition containing the acrylonitrile has been found to exhibit a yellowness which has become increasingly unacceptable over the years since the issuance of said patent. Furthermore, acrylonitrile has recently been determined to be a carcinogen which renders it undesirable as a component in compositions used to manufacture food packaging.